An electronic product including a touch device is characterized as being easy to use. Therefore, the touch device has become an important unit of the electronic product. Categorizing by operating principles, the known touch devices can be categorized into capacitive, resistive, and optical touch devices. Taking optical touch devices as an example, a conventional optical touch device includes a light emitting unit, a light guide plate, and an infrared light image capturing device. When a user does not touch the optical touch device, an infrared light beam emitted by the light emitting unit is confined in the light guide plate, and the infrared light image capturing device does not detect the infrared light beam emitted from the light emitting unit. When the user touches the optical touch device, a total internal reflection of the infrared light beam in the light guide plate is destroyed. At this moment, the infrared light beam is reflected by a finger of the user and the infrared light beam is further transmitted into the infrared image capturing device. The conventional optical touch device then analyzes the infrared light image captured by the infrared light image capturing device to determine the position touched by the finger of the user. However, when the conventional optical touch device is used in an outdoor setting, an infrared light component in an ambient light beam tends to penetrate through the light guide plate to be transmitted into the infrared light image capturing device, causing a decreased reliability and sensitivity of the conventional optical touch device.
U.S. Patent Publication No. 20100302210 has disclosed a touch screen device including an infrared light source, a light guide plate, a bendable frustrating layer, an image detector and a projection source. U.S. Patent Publication No. 20080179507 has disclosed a multi-touch sensing device including a bendable layer, a light guide plate, an infrared light source, an image detector, and a projector. U.S. Patent Publication No. 20080284925 has disclosed a multi-touch sensing device including an infrared light emitter, a light guide board, a cover layer, an infrared light filter, and a liquid crystal panel.